Permanent magnet rotating electric machine and electrically driven vehicle employing same

ABSTRACT

A rotating electric machine comprises a stator having stator salient poles, three-phases windings wound around said stator salient poles, a rotor rotatable held inside the said stator, and permanent magnets inserted into said rotor and positioned opposite to said stator salient poles, wherein said three-phase windings are concentratively wound around each of said stator salient poles, said windings of each phase are wound around at more than one stator salient pole, and said windings of each phase have a phase difference of voltage between at least one of the windings and the other.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a permanent magnetrotating electric machine and an electrically driven vehicle employingsame.

[0003] 2. Description of Related Art

[0004] Motors used in electrically driven vehicles, in particular,driving electric cars must ensure a sufficient running distance with alimited battery capacity, so that they are desired to be small,light-weight, and highly efficient.

[0005] For a motor to be small and light weight, it is required to besuitable for high speed rotation. In this regard, permanent magnetmotors are advantageous over direct-current motors and induction motor.

[0006] Permanent magnet rotors are classified into a surface magnetrotor which has permanent magnets positioned along the outer peripheryof the rotor and a so-called internal magnet rotor which has a permanentmagnet holder within a core made of silicon steel or the like having ahigher magnetic permeability than permanent magnets.

[0007] The surface magnet rotor is advantageous in ease of control, lessinfluences by reactive magnetic flux of a stator winding, low noise, andso on. However, the surface magnet rotor also has several disadvantagessuch as requirement of reinforced magnets for high speed rotation, anarrow speed control range due to difficulties in field weakeningcontrol, a low efficiency in high speed and low load operations, and soon.

[0008] The internal magnet rotor, in turn, has advantages such as thecapability of high speed rotation by field weakening control usingmagnetic pole pieces positioned along the outer periphery of magnets,the capability of highly efficient rotation in high speed and low loadoperations, utilization of reluctance torque, and so on.

[0009] Prior art internal magnet rotors are described, for example, inJP-A-5-219669, FIG. 5 of JP-A-7-39091.

[0010] Within large-size permanent magnet motors used in electricvehicles and so on, those having an internal permanent magnet rotoremploy a distributed winding stator for their stator structure.

[0011] However, permanent magnet motors described in the prior art havea disadvantage that pulsating torque based on high frequency componentsof permanent magnets or auxiliary magnet poles is produced. Also,cogging torque is produced by influence of roughness and fineness ofmagnetic flux of stator salient poles and roughness and fineness ofmagnetic flux of permanent magnets, and smooth rotation of permanentmagnet motors cannot be obtained. Further, since the distributed windingstator has elongated winding ends, this causes a limitation to reductionin size and weight of rotating electric machines employing a distributedwinding stator.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a permanentmagnet rotating electric machine which has small pulsating torque andcogging torque, and can be obtained smooth rotation thereof.

[0013] It is another object of the present invention to provide apermanent magnet rotating electric machine having shortened windingends, and having stator construction being capable to be small,light-weight.

[0014] To achieve the above object, according to a first aspect, thepresent invention provides a permanent magnet rotating electric machinecomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatably held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said windings of each phase havea phase difference of voltage between at least one of the windings andthe other.

[0015] Preferably, the permanent magnet rotating electric machinesatisfies M:P=6n:6n±2, where M is the number of the stator salientpoles, P is the number of the permanent magnets, and n is a positiveinteger.

[0016] Preferably, the permanent magnet rotating electric machinesatisfies M:P=3n:3n±1, where M is the number of the stator salientpoles, P is the number of the permanent magnets of the rotor, and n is apositive integer.

[0017] Preferably, in the permanent magnet rotating electric machine,the number of poles of the permanent magnets is eight or more.

[0018] Preferably, in the permanent magnet rotating electric machine, amagnetic pole piece area of the rotor is projected toward the stator.

[0019] Preferably, in the permanent magnet rotating electric machine, amagnetic material having a higher magnetic impermeability than thepermanent magnets is disposed between adjacent ones of the permanentmagnets.

[0020] To achieve the above object, according to a second aspect, thepresent invention provides a permanent magnet rotating electric machinecomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatable held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles.

[0021] To achieve the above object, according to an aspect, the presentinvention provides an electrically driven vehicle comprising a permanentmagnet rotating electric machine being coupled to drive wheelscomprising a stator having stator salient poles, three-phases windingswound around said stator salient poles, a rotor rotatable held insidethe said stator, and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, and control means forsupplying a voltage to said three-phase windings, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said control means suppliesvoltage which has a phase difference between at least one of thewindings and the other among each phase of three-phase.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a partial cross-sectional view of a permanent magnetrotating electric machine according to a first embodiment of the presentinvention, viewed from the front side thereof;

[0023]FIG. 2 is a cross-sectional view taken along the section line A-Aof FIG. 1, illustrating the permanent magnet rotating electric machineaccording to the first embodiment of the present invention;

[0024]FIG. 3 is a circuit diagram illustrating a control circuit for thepermanent magnet rotating electric machine according to the firstembodiment of the present invention;

[0025] FIGS. 4A-4C are explanatory diagrams illustrating torquegenerated by the permanent magnet rotating electric machine according tothe first embodiment of the present invention;

[0026] FIGS. 5A-5C are diagrams for explaining the principles of thepermanent magnet rotating electric machine according to the firstembodiment of the present invention;

[0027]FIG. 6 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a second embodiment of thepresent invention;

[0028]FIG. 7 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a third embodiment of the presentinvention;

[0029]FIG. 8 is a cross-sectional view illustrating a permanent magnetrotating electric machine according to a fourth embodiment of thepresent invention; and

[0030]FIG. 9 is a block diagram illustrating an electric car equippedwith a permanent magnet rotating electric machine according to a fifthembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Permanent magnet rotating electric machines according to a firstembodiment of the present invention will hereinafter be described withreference to FIGS. 1-5C.

[0032]FIG. 1 is a partial cross-sectional view of a permanent magnetrotating electric machine according to a first embodiment of the presentinvention, viewed from the front side thereof.

[0033] Referring specifically to FIG. 1, a stator 20 of a rotatingelectric machine 10 comprises a stator core 22, multi-phase statorwindings 24 wound around the stator core 22, and a housing 26 forsecurely holding the stator core 22 on the inner peripheral surfacethereof. A rotor 30 comprises a rotor core 32, permanent magnets 36inserted into permanent magnet inserting holes 34 formed in the rotorcore 32, and a shaft 38. The shaft 38 is rotatable held by bearings 42,44. The bearings 42, 44 are supported by end brackets 46, 48,respectively, which in turn is secured to both ends of the housing 26.

[0034] A magnetic pole position detector PS for detecting the positionof the permanent magnets 36 of the rotor 30 and an encoder E fordetecting the position of the rotor 30 are disposed on a side surface ofthe rotor 30. The operation of the rotating electric machine 10 iscontrolled by a control unit, later described with reference to FIG. 3,in response to a signal of the magnetic pole position detector PS and anoutput signal of the encoder E.

[0035]FIG. 2 is a cross-sectional view taken along the section line A-Aof FIG. 1, wherein however, the illustration of the housing 26 isomitted.

[0036] Referring specifically to FIG. 2, the rotating electric machine10 comprises the stator 20 and the rotor 30. The rotor 20 comprises thestator core 22 and the stator windings 24. The stator core 22 comprisesan annular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, the length ofend coil portions can be reduced, and consequently the physical size ofthe rotating electric machine can also be reduced. The end coil portionsrefer to portions of the stator windings 24 projecting from the statorcore 24 to the left and right directions in FIG. 1. Since these end coilportions can be reduced, the entire rotating electric machine can bereduced in length, thus resulting in a smaller size of the rotatingelectric machine.

[0037] The U-phase of the stator windings 24 is connected to U1+, U1−,U2+, U2−, respectively; the V-phase is connected to V1+, V1−, V2+, V2−,respectively; and W-phase is connected to W1+, W1−, W2+, W2−,respectively.

[0038] The rotor 30 comprises a rotor core 32 formed of a plurality oflaminated plates made of a highly magnetically permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor core 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

[0039] The rotor core 32 is formed with the permanent magnet insertingholes 34 and a hole for passing the shaft 38 therethrough, both formedby punch press. Thus, the rotor 30 is composed of the rotor core 32 madeof laminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

[0040] The rotor core 32 may be divided in the radial direction into aninner yoke area 32A and an outer peripheral area 32B. The outerperipheral area 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux Bφ from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to formmagnetic circuits.

[0041] The permanent magnets 36 can be accommodated in the permanentmagnet inserting holes 34 which are bordered by the auxiliary magneticpole area 32B1 in the circumferential direction and bordered by themagnetic pole piece area 32B2 around the outer periphery, thus providinga motor suitable for high speed rotation.

[0042] The concentrated winding stator is generally used in reluctancemotors and small brash-less motors. In this case, the reluctance motorincludes a rotor only having auxiliary magnetic poles, while thebrash-less motor has permanent magnets directly disposed on the outersurface of a rotor. Thus, the reluctance motor generate small torqueincluding large pulsating components.

[0043] With the surface magnetic rotor, on the other hand, it isrelatively difficult to apply a field weakening control thereto.Accordingly the surface magnetic rotor is likely to cause a loss due toan eddy current generated in surface magnets to reduce the efficiency.

[0044] In contrast, a structural combination of a rotor employinginternal permanent magnets and a concentrated winding stator allows forutilization of torque generated by flux of the permanent magnets as wellas torque generated by reluctance components of the auxiliary magneticpoles, thereby providing a higher efficiency. In addition, since thefield weakening can be achieved by the effect of the auxiliary magneticpoles, later described, an operating region can be significantlyexpanded, particularly, in a high speed region.

[0045] Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the first embodiment is free from eddy current losses.

[0046] It is assumed in the example illustrated in FIG. 2 that therotating electric machine is a three-phase motor which comprises thepermanent magnet rotor 36 with the number of poles being ten, and thestator with the number of magnetic poles being twelve. When the numberof stator salient poles is represented by M and the number of the polesof the rotor magnets by P, a structure satisfying the followingrelationship:

[0047] M:P=6n:6n±2 (where n is a positive integer) can realize reducedtorque pulsations and an increased utilization ratio of windings(winding coefficient). It is therefore appreciated that the embodimentillustrated in FIG. 2 can provide a highly efficient, small andlight-weight rotating electric machine.

[0048] It goes without saying that while the foregoing description hasbeen made in connection with an example of a motor, the first embodimentcan be similarly applied to a generator.

[0049] Next, a control unit for controlling the permanent magnetrotating electric machine according to the first embodiment will bedescribed with reference to FIG. 3.

[0050]FIG. 3 is a circuit diagram of a control circuit for the permanentmagnet rotating electric machine according to the first embodiment.

[0051] The stator windings 24 of the rotating electric machine 24 arepowered from a direct current power source 80 through an invertor 82. Aspeed control circuit (ASR) 84 calculates a speed difference {overscore(ω)}e from a speed instruction {overscore (ω)}s and an actual speed{overscore (ω)}f derived from positional information θ from the encoderE through an F/V convertor 86, and outputs a torque instruction inaccordance with a PI control scheme (P represents a proportional term,and I an integral term) or the like, i.e., a current instruction Is anda rotating angle θ1 for the rotor 30.

[0052] A phase shift circuit 88 shifts the phase of pulses from theencoder E, i.e., the positional information θ from the encoder E inaccordance with the rotating angle θ1 instructed from the speed controlcircuit (ASR) 84. A sine wave/cosine wave generator 90 generates a sinewave output by shifting the phase of an induced voltage of each of thestator windings 24 (three phases in this embodiment) based on theposition detector PS for detecting the positions of the magnetic polesof the permanent magnets of the rotor 30 and the positional informationθ on the rotor 30 having its phase shifted by the phase shift circuit88. The amount of phase shift may be zero.

[0053] A two-phase/three-phase convertor circuit 92 outputs currentinstructions Isa, Isb, Isb to the respective phases in accordance withthe current instruction Is from the speed control circuit (ASR) 84 andan output of the sin wave/cosine wave generator 90. The respectivephases individually have current control systems (ACR) 94A, 94B, 94Cwhich control respective phase currents by providing the invertor 82with signals in accordance with the current instructions Isa, Isb, Iscand current detecting signals Ifa, Ifb, Ifc. In this event, a combinedcurrent of the respective phase currents is always formed at a positionperpendicular to the field flux or at a phase shifted position, so thatcharacteristics equivalent to those of a direct current motor can beachieved without commutator.

[0054] When the rotating electric machine of the first embodiment isapplied to an electric car, the control unit has a torque control systemfor directly controlling the torque instead of the speed control circuit84. In other words, the speed control circuit 84 is replaced with atorque control circuit. The torque control circuit receives torque Ts asan input signal, calculates torque Te from the torque Ts and actualtorque Tf detected by a torque detector, and outputs a torqueinstruction in accordance with a PI control scheme (P represents aproportional term, and I an integral term) or the like, i.e., a currentinstruction Is and a rotating angle θ1 for the rotor 30.

[0055] In a permanent magnet rotating electric machine, since torque isdirectly proportional to a current, a current control system may beprovided instead of the speed control circuit 84.

[0056] The connection of the stator windings 24 is made in accordancewith a three-phase stator winding scheme. More specifically, U1+, U1−,U2+, U2− are connected in the illustrated order in the U-phase; V1+, V−,V2+, V2− are connected in the illustrated order in the V-phase; and W1+,W1−, W2+, W2− are connected in the illustrated order in the W-phase.Here, between the windings constituting the respective phases, forexample, between U1+ and U2−, and between U1− and U2+ in the U-phase;between V1+ and V2−, and between V1− and V2+ in the V-phase; and betweenW1+ and W2−, and between W1− and W2+ in the W-phase, there is a phasedifference of 30 degrees in electrical angle. Specifically explainingwith reference to FIG. 2, for example, an angle θ1 between the statorsalient poles U1+ and U2− is 30 degrees, while adjacent permanentmagnets 36 of the rotor 30 are angularly spaced by angles θ2. In thisway, within the stator salient poles which are wound by the statorwindings connected to the same phase, at least one stator salient polehas a phase shifted with respect to the associated permanent magnet.Take, as an example, a stator salient pole around which the winding U1−is wound and a stator salient pole around which the winding U2+ iswound. Assuming that U1− is in phase with the permanent magnet 36A, U1−is shifted from the permanent magnet 36B by an angular distance of 30degrees. This contributes to a reduction in pulsating pulse which maycause a problem in the concentrated winding stator. The reason for thisreduction will be described later with reference to FIG. 4.

[0057] A concentrated winding should be constructed such that respectivewindings do not overlap on the gap surface as illustrated in FIG. 1.This eliminates interference between the respective windings, and asmall, light-weight and simple rotating electric machine can berealized.

[0058] Also, by selecting adjacent windings to be connected to the samephase as illustrated, the connection is facilitated. Specifically, inthe U-phase, U1+ and U2− are adjacent, and U1− and U2+ are adjacent. Inthe V-phase, V1+ and V2− are adjacent, and V− and V2+ are adjacent.Similarly, in the W-phase, W1+ and W2− are adjacent, and W1+ and W2+ areadjacent, thus facilitating the connection of these windings.

[0059] Next, the reason for the reduction in torque pulsation will beexplained with reference to FIGS. 4A-4C.

[0060] FIGS. 4A-4C show the torque generated by the permanent magnetrotating electric machine according to the first embodiment of thepresent invention.

[0061]FIG. 4A represents torque which is generated when the respectivestator windings of U1+, U1−, V1+, V1−, W1+, W1− are applied with a sinewave current based on a signal from the sine wave/cosine wave generatorcircuit 90 illustrated in FIG. 3. While uniform torque would begenerated if no harmonics were included, the inclusion of harmoniccomponents caused by the permanent magnets, harmonic components due tothe auxiliary magnetic poles, and so on cause torque pulsation at aperiod of 60 degrees in electrical angle, as illustrated.

[0062]FIG. 4B represents torque which is generated when the respectivestator windings of U2+, U2−, V2+, V2−, W2+, W2− are applied with a sinewave current. Since the represented torque includes harmonic componentscaused by the permanent magnets, harmonic components due to theauxiliary magnetic poles, and so on, as is the case of the torquerepresented in FIG. 4A, torque pulsations are generated at a period of60 degrees in electrical angle.

[0063] It should be noted herein that since there is a phase differenceof 30 degrees in electrical angle between the stator salient polesaround which U1+, U1−, V1+, V1−, W1+, W1− of the stator windings 24 arewound and the stator salient poles around which U2+, U2−, V2+, V2−, W2+,W2− of the stator windings 24 are wound, the torque pulsations generatedthereby are in opposite phase to each other.

[0064] Thus, a combination of torque of FIGS. 4A and 4B exhibits reducedpulsations as shown in FIG. 4C.

[0065] Referring back to FIG. 2, in the example in which the ratio ofthe number of permanent magnet M to the number of stator salient poles Pis determined to be 10:12, the cogging torque of the permanent magnetrotating electric machine exhibits a number of pulsations per rotationequal to the least common multiple of the number of permanent magnetsand the number of stator salient poles , i.e.,60 per rotation in thisexample. Generally, the cogging torque is smaller as the number ofpulsations per rotation is larger.

[0066] In a conventionally used motor having a general surface magnetrotor and a concentrated winding stator, the ratio of the number ofpermanent magnets M to the number of stator salient poles P is typically2:3. This ratio corresponds to 10:15 when the number of permanentmagnets M is changed from two to ten which is the number of permanentmagnets M in the example illustrated in FIG. 2. In this case, the numberof pulsations per rotation of the cogging torque is calculated to be 30which is the least common multiple of 10 and 15. It will be understoodfrom this discussion that the structure of the first embodiment canreduce the cogging torque more than conventional motor of the same type.

[0067] In addition, pulsating torque possibly occurring when a currentis conducted can be reduced by the principles shown in FIG. 4.

[0068] Next, the operation principles of the field weakening control forthe permanent magnet rotating electric machine according to the firstembodiment will be explained with reference to FIGS. 5A-5C.

[0069] Torque T generated by a permanent magnet rotating electricmachine is generally expressed by the following equation:

T={E 0 ·Iq+(Xq−Xd)·Id·Iq}/w

[0070] where E0 is an induced voltage; Xq is reactance on q-axis; Xd isreactance on d-axis; Id is a current on d-axis; Iq is a current onq-axis; and w is an angular rotational speed.

[0071] Referring first to FIG. 5A, a permanent magnet 36 is positionedon d-axis, and an auxiliary magnetic pole area 32B1 having a highermagnetic permeability than the permanent magnet 36 is positioned onq-axis. In this arrangement, respective vectors are represented in FIG.5A. A current Im, which is a combination of the d-axis current Id andthe q-axis current Iq, is controlled in the illustrated direction by thecurrent instructions Isa, Isb, Isc generated by the control circuitillustrated in FIG. 3, calculations of output positions of the magneticpole position detector PS and the encoder E of the rotating electricmachine, and so on.

[0072] In the foregoing equation, the first term expresses a componentof torque generated by the permanent magnet, and the second termexpresses a reluctance component generated by the auxiliary magneticpole area 32B1.

[0073] A rotating electric machine for electric car must be controlledso as to maximize the torque/current particularly during a low speedoperation. FIG. 5A shows a vector diagram when the rotating electricmachine is controlled to generate a maximum torque current. In thisevent, the rotating electric machine is controlled to apply an increasedmagnetomotive force to the auxiliary magnetic pole 32B1, thus takingadvantage of the torque generated by the permanent magnet, expressed bythe first term, as well as the reluctance torque generated by theauxiliary magnetic pole 32B1, expressed by the second term.

[0074] In a high speed region, on the other hand, the torque may besmall. Rather, the Id component is increased to cancel the inducedvoltage E0 of the permanent magnet by Xd·Id in order to weaken the fluxof the permanent magnet 36, whereby the rotating electric machine can berotated up to a high speed region. FIG. 5B shows a vector diagram duringa high speed operation.

[0075] The currents Id, Iq are controlled by the phase shift circuit 88of the control circuit illustrated in FIG. 3.

[0076] Referring next to FIG. 5C, a broken line T2 represents torquegenerated by a conventional surface magnet rotating electric machine. Itcan be seen from the broken line T2 that the torque is decreased in ahigh speed region. A solid line T1, in turn, represents the relationshipbetween the torque and the speed of the permanent magnet rotatingelectric machine according to the first embodiment, provided by thecontrol described above. Since the current can more easily pass throughas compared with the conventional surface magnet rotating electricmachine, the permanent magnet rotating electric machine of the firstembodiment can be operated in a higher speed region.

[0077] According to the first embodiment, since a concentrated windingstator is employed, the end coil portions of the stator can be reduced,so that a smaller rotating electric machine can be provided.

[0078] Also, since the stator salient poles, having wound therearoundthe stator windings connected to the same phase, include at least onesalient pole which has a different phase with respect to the associatedpermanent magnet, this configuration reduces the pulsating torque whichmay cause a problem in the concentrated winding stator.

[0079] Further, since the permanent magnet rotor is provided withauxiliary magnetic poles, a structure suitable for field weakeningcontrol is realized, thereby providing a rotating electric machineappropriate to high speed rotation.

[0080] Furthermore, since an auxiliary magnetic pole area made of amagnetic material having a higher magnetic permeability than thepermanent magnets is positioned between the permanent magnets, increasedtorque can be generated.

[0081] Moreover, the permanent magnets are surrounded by silicon steelplates, so that a structure suitable for high speed rotation can beprovided.

[0082] Next, a permanent magnet rotating electric machine according toanother embodiment of the present invention will be described withreference to FIG. 6.

[0083]FIG. 6 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to a second embodiment of thepresent invention.

[0084] The second embodiment is characterized by a three-phase motorstructure which comprises a permanent magnet rotor 36 having ten poles(P=10) and a stator having nine magnetic poles (M=9). Thus, when theratio of the number of stator salient poles M to the number of magneticpoles of the stator magnet P (M:P) is 3n:3n±1, reduced torque pulsationsand an increased utilization ratio of windings (winding coefficient) canbe realized, so that a highly efficient, small, and light-weightrotating electric machine can be provided.

[0085] Referring specifically to FIG. 6, the rotating electric machine10 comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, the length ofend coil portions can be reduced, and consequently the physical size ofthe rotating electric machine can also be reduced.

[0086] The U-phase of the stator windings 24 is connected to U1+, U1−,U2+, U2−, respectively; the V-phase is connected to V1+, V1−, V2+, V2−,respectively; and W-phase is connected to W1+, W1−, W2+, W2−,respectively.

[0087] The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

[0088] The rotor core 32 is formed with the permanent magnet insertingholes 34 and a hole for passing the shaft 38 therethrough, both formedby punch press. Thus, the rotor 30 is composed of the rotor core 32 madeof laminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

[0089] The rotor core 32 may be divided in the radial direction into aninner yoke area 32A and an outer peripheral area 32B. The outerperipheral area 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux B1 from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to form amagnetic circuit.

[0090] The permanent magnets 36 can be accommodated in the permanentmagnet inserting holes 34 which are bordered by the auxiliary magneticpole area 32B1 in the circumferential direction and bordered by themagnetic pole piece area 32B2 around the outer periphery, thus providinga rotating electric machine suitable for high speed rotation.

[0091] Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

[0092] It is assumed in the example illustrated in FIG. 6 that therotating electric machine is a three-phase motor which comprises thepermanent magnet rotor 36 with the number of poles P being ten, and thestator with the number of magnetic poles being nine. When the number ofstator salient poles is represented by M and the number of the poles ofthe rotor magnets by P, a structure satisfying the followingrelationship:

[0093] M:P=3n:3n±1 (where n is a positive integer) can realize reducedtorque pulsations and an increased utilization ratio of windings(winding coefficient), so that a highly efficient, a small andlight-weight rotating electric machine can be provided.

[0094] The connection of the stator windings 24 is made in accordancewith a three-phase stator winding scheme. More specifically, U1+, U1−,U2+ are connected in the illustrated order in the U-phase; V1+, V1−, V2+are connected in the illustrated order in the V-phase; and W1+, W1−, W2+are connected in the illustrated order in the W-phase. Here, thewindings constituting the respective phases, for example, U1+ and U1−,and U1− and U2+ in the U-phase; V1+ and V1−, V1− and V2+ in the V-phase;and W1+ and W1−, W1− and W2+ in the W-phase, have a phase difference of20 degrees in electrical angle. In this way, the stator salient poleshaving wound therearound the stator windings connected to the samephase, increase at least one stator salient pole which has a differentphase with respect to the associated permanent magnet. Take, as anexample, a stator salient pole having wound therearound the winding U1−and a stator salient pole having wound therearound the winding U2+.Assuming that U1− is in phase with the permanent magnet 36A, U1− isshifted from the permanent magnet 36B by an angular distance of 30degrees. This contributes to a reduction in pulsating torque which maycause a problem in the concentrated winding stator.

[0095] An electrical angle between adjacent stator salient poles 22B iscalculated to be 200 degrees (180×(10/9)=200), and 20 degrees whentaking into account the phase difference. The cogging torque of thepermanent magnet rotating electric machine exhibits a number ofpulsations per rotation equal to the least common multiple of the numberof permanent magnets and the number of stator salient poles , i.e., 90per rotation in this example.

[0096] In the example illustrated in FIG. 2 in which the ratio of thenumber of permanent magnets M to the number of stator salient poles P is10:12, the cogging torque of the permanent magnet rotating electricmachine exhibits pulsations of 60 per rotation. It is understood fromthis discussion that the second embodiment can further reduce thecogging torque.

[0097] It goes without saying that while the foregoing description hasbeen made in connection with an example of a motor, the secondembodiment can be similarly applied to a generator.

[0098] According to the second embodiment, since a concentrated windingstator is employed, the end coil portions of the stator can be reducedin length, so that a smaller rotating electric machine can be provided.

[0099] Also, since the stator salient poles, having wound therearoundstator windings connected to the same phase, include at least onesalient pole which has a different phase with respect to the associatedpermanent magnet, this configuration reduces the pulsating torque whichmay cause a problem in the concentrated winding stator.

[0100] In addition, the cogging torque can be further reduced.

[0101] Further, since the permanent magnet rotor is provided withauxiliary magnetic poles, a structure suitable for field weakeningcontrol is realized, thereby providing a rotating electric machineappropriate to high speed rotations.

[0102] Furthermore, since an auxiliary magnetic pole area made of amagnetic material having a higher magnetic permeability than thepermanent magnets is positioned between the permanent magnets, increasedtorque can be generated.

[0103] Moreover, the permanent magnets are surrounded by silicon steelplates, so that a rotating electric machine suitable for high speedrotations can be provided.

[0104] Next, a permanent magnet rotating electric machine according to athird embodiment of the present invention will be described withreference to FIG. 7.

[0105]FIG. 7 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to the third embodiment of thepresent invention.

[0106] The third embodiment is characterized by a three-phase motorstructure which comprises a permanent magnet rotor 36 having twelvepoles (P=12) and a stator having eight magnetic poles (M=8). Since thisstructure can increase the utilization ratio of windings (windingcoefficient), a highly efficient, small, and light-weight rotatingelectric machine can be provided.

[0107] Referring specifically to FIG. 7, the rotating electric machine10 comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, end coilportions can be reduced in length, and consequently the physical size ofthe rotating electric machine can also be reduced.

[0108] The U-phase of the stator windings 24 is connected to U1, U2, U3,U4, respectively; the V-phase is connected to V1, V2, V3, V4,respectively; and W-phase is connected to W1, W2, W3, W4, respectively.

[0109] The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

[0110] The rotor core 32 is formed with the permanent magnet insertingholes 34 and a hole for passing the shaft 38 therethrough, both formedby punch press. Thus, the rotor 30 is composed of the rotor core 32 madeof laminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

[0111] The rotor core 32 may be divided in the radial direction into aninner yoke area 32A and an outer peripheral area 32B. The outerperipheral area 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. The magnetic pole piecearea 32B2 is an area positioned outside the permanent magnets 36 withinthe outer peripheral area 32B of the rotor core 32, in which magneticflux Bφ from the permanent magnets 36 flows through gaps between thepermanent magnets 36 and the stator 20 into the stator 20 to form amagnetic circuit.

[0112] The permanent magnets 36 can be accommodated in the permanentmagnet inserting holes 34 which are bordered by the auxiliary magneticpole area 32B1 in the circumferential direction and bordered by themagnetic pole piece area 32B2 around the outer periphery, thus providinga rotating electric machine suitable for high speed rotation.

[0113] Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

[0114] It is assumed in the example illustrated in FIG. 7 that therotating electric machine is a three-phase motor which comprises thepermanent magnet rotor 36 with the number of poles P being twelve, andthe stator with the number of magnetic poles being eight. Since such astructure achieves an increased utilization ratio of the windings(winding coefficient), a highly efficient, small and light-weightrotating electric machine can be provided.

[0115] The connection of the stator windings 24 is made in accordancewith a three-phase stator winding scheme. More specifically, U1, U2, U3,U4 are connected in the illustrated order in the U-phase; V1, V2, V3, V4are connected in the illustrated order in the V-phase; and W1, W2, W3,W4 are connected in the illustrated order in the W-phase. The windingsforming parts of the U-phase, V-phase, W-phase have a phase differenceof 60 degrees between each other.

[0116] In the third embodiment, the stator salient poles having woundtherearound the stator windings connected to the same phase are in phasewith the associated permanent magnets, so that a reduction in torquepulsation is not expected. However, since the salient poles in phasewith the permanent magnets are positioned in a symmetric configuration,a well balanced structure can be provided. More specifically explainingwith reference to the U-phase, the respective salient poles U1, U2, U3,U4 are positioned symmetrically about the shaft 38.

[0117] It goes without saying that while the foregoing description hasbeen made in connection with an example of a motor, the third embodimentcan be similarly applied to a generator.

[0118] According to the third embodiment, since a concentrated windingstator is employed, the end coil portions of the stator can be reducedin length, so that a smaller rotating electric machine can be provided.

[0119] Also, since the permanent magnet rotor is provided with auxiliarymagnetic poles, a structure suitable for field weakening control isrealized, thereby providing a rotating electric machine appropriate tohigh speed rotations.

[0120] Further, since an auxiliary magnetic pole area made of a magneticmaterial having a higher magnetic permeability than the permanentmagnets is positioned between the permanent magnets, increased torquecan be generated.

[0121] Moreover, the permanent magnets are surrounded by silicon steelplates, so that a rotating electric machine suitable for high speedrotations can be provided.

[0122] Next, a permanent magnet rotating electric machine according to afourth embodiment of the present invention will be described withreference to FIG. 8.

[0123]FIG. 8 is a cross-sectional view illustrating the permanent magnetrotating electric machine according to the fourth embodiment of thepresent invention.

[0124] The fourth embodiment is characterized by a three-phase motorstructure which comprises a permanent magnet rotor 36 having twelvepoles (P=12) and a stator having eight magnetic poles (M=8). Since thisstructure can increase the utilization ratio of windings (windingcoefficient), a highly efficient, small, and light-weight rotatingelectric machine can be provided.

[0125] In addition, a magnetic pole piece area of the rotor is projectedtoward the magnetic poles of the stator, such that a sinusoidal magneticflux distribution is produced.

[0126] Referring specifically to FIG. 8, the rotating electric machine10 comprises a stator 20 and a rotor 30. The rotor 20 comprises a statorcore 22 and a stator windings 24. The stator core 22 comprises anannular stator yoke 22A and stator salient poles 22B, and the statorwindings 24 are concentratively wound around the stator salient poles22B. The respective windings 24 are configured not to share a magneticpath on gap surfaces. By employing a stator structure in which thestator windings are implemented by concentrated windings, end coilportions can be reduced in length, and consequently the physical size ofthe rotating electric machine can also be reduced.

[0127] The U-phase of the stator windings 24 is connected to U1, U2, U3,U4, respectively; the V-phase is connected to V1, V2, V3, V4,respectively; and W-phase is connected to W1, W2, W3, W4, respectively.

[0128] The rotor 30 comprises a rotor core 34 formed of a plurality oflaminated plates made of a highly magnetic permeable material, forexample, silicon steel; four permanent magnets 36 inserted into fourpermanent magnet inserting holes 34 formed in the rotor cores 32; and ashaft 38. Ten permanent magnets 36 are positioned in the circumferentialdirection of the rotor core 32 at equal intervals such that theirpolarities are in the opposite directions from each other.

[0129] The rotor core 32 is formed with the permanent magnet insertingholes 34 and a hole for passing the shaft 38 therethrough, both formedby punch press. Thus, the rotor 30 is composed of the rotor core 32 madeof laminated silicon steel plates and formed with the punch-pressedpermanent magnet inserting holes 34 and hole for passing the shaft 38therethrough, the permanent magnets 36 inserted into the holes 34, andthe shaft 38 extending through the hole.

[0130] The rotor core 32 may be divided in the radial direction into aninner yoke area 32A and an outer peripheral area 32B. The outerperipheral area 32B of the rotor core 32 may be further divided in thecircumferential direction into an auxiliary magnetic pole area 32B1 anda magnetic pole piece area 32B2. The auxiliary magnetic pole area 32B1,which is an area sandwiched by adjacent permanent magnet inserting holes34, functions to prohibit magnetic circuits of the magnets from passingtherethrough and to allow magnetic flux to be directly generated in thestator by a magnetomotive force of the stator. In the fourth embodiment,the magnetic pole piece area of the rotor is projected toward the statormagnetic poles 22B to shape a sinusoidal magnetic flux distribution.

[0131] The permanent magnets 36 can be accommodated in the permanentmagnet inserting holes 34 which are bordered by the auxiliary magneticpole area 32B1 in the circumferential direction and bordered by themagnetic pole piece area 32B2 around the outer periphery, thus providinga rotating electric machine suitable for high speed rotation.

[0132] Further, since the magnetic pole piece area is made of a magneticmaterial, pulsating flux from the stator salient poles can be mitigated.Also, since the laminated steel core is employed, the rotating electricmachine of the second embodiment is free from eddy current losses.

[0133] It is assumed in the example illustrated in FIG. 8 that therotating electric machine is a three-phase motor which comprises thepermanent magnet rotor 36 with the number of poles P being twelve, andthe stator with the number of magnetic poles being eight. Since such astructure achieves an increased utilization ratio of the windings(winding coefficient), a highly efficient, small and light-weightrotating electric machine can be provided.

[0134] The connection of the stator windings 24 is made in accordancewith a three-phase stator winding scheme. More specifically, U1, U2, U3,U4 are connected in the illustrated order in the U-phase; V1, V2, V3, V4are connected in the illustrated order in the V-phase; and W1, W2, W3,W4 are connected in the illustrated order in the W-phase. The windingsforming parts of the U-phase, V-phase, W-phase have a phase differenceof 60 degrees between each other.

[0135] In the fourth embodiment, the stator salient poles, having woundtherearound the stator windings connected to the same phase, are inphase with the associated permanent magnets, so that a reduction intorque pulsation is not expected. However, since the salient poles inphase with the permanent magnets are positioned in a symmetricconfiguration, a well balanced structure can be provided. Morespecifically explaining with reference to the U-phase, the respectivesalient poles U1, U2, U3, U4 are positioned symmetrically about theshaft 38.

[0136] It goes without saying that while the foregoing description hasbeen made in connection with an example of a motor, the fourthembodiment can be similarly applied to a generator.

[0137] According to the fourth embodiment, since a concentrated windingstator is employed, the end coil portions of the stator can be reducedin length, so that a smaller rotating electric machine can be provided.

[0138] Also, since the permanent magnet rotor is employed, a structuresuitable for field weakening control is realized, thereby providing arotating electric machine appropriate to high speed rotations.

[0139] Moreover, the permanent magnets are surrounded by silicon steelplates, so that a rotating electric machine suitable for high speedrotations can be provided.

[0140] While the foregoing respective embodiments have been described inconnection with a control system which controls a sinusoidal currentwith respect to the position of the rotor, it goes without saying thatthe present invention may also be applied to a 120 degree conductivebrash-less motor scheme which does not perform a current control.

[0141] Also, while the foregoing description has been made withreference to an internal rotation type motor, the present invention mayalso be applied to external rotation type motors, generators, and linearmotors.

[0142] Next, an electric car employing a permanent magnet rotatingelectric machine according to a fifth embodiment will be described withreference to FIG. 9.

[0143]FIG. 9 is a block diagram illustrating the configuration of anelectric car which is equipped with a permanent magnet rotating electricmachine according to the fifth embodiment of the present invention.

[0144] A body 100 of the electric car is supported by four wheels 110,112, 114, 116. Since this electric car is a front-wheel driven type, apermanent magnet rotating electric machine 120 is directly coupled to afront wheel shaft 154. The permanent magnet rotating electric machine120 has a structure as illustrated in FIG. 2, 6, 7 or 8. A control unit130 is provided for controlling driving torque of the permanent magnetrotating electric machine 120. A battery 140 is provided as a powersource for the control unit 130. Electric power from the battery 140 issupplied to the permanent magnet rotating electric machine 120 throughthe control unit 130, thereby driving the permanent magnet rotatingelectric machine 120 to rotate the wheels 110, 114. The rotation of asteering wheel 150 is transmitted to the two wheels 110, 114 through atransmission mechanism including a steering ring gear 152, a tie rod, aknuckle arm, and so on to change the angle of the wheels 110, 114.

[0145] It should be noted that while in the foregoing embodiment, thepermanent magnet rotating electric machine has been described to be usedfor driving wheels of an electric car, the permanent magnet rotatingelectric machine may also be used for driving wheels of an electriclocomotive or the like.

[0146] According to the fifth embodiment, when the permanent magnetrotating electric machine is applied to an electrically driven vehicle,particular to an electric car, a small, light-weight, and highlyefficient permanent magnet rotating electric machine can be equipped inthe vehicle, thus making it possible to provide an electric car whichcan run a longer distance with the amount of electric power accumulatedin one recharging operation.

What is claimed is:
 1. A permanent magnet rotating electric machinecomprising: a stator having stator salient poles, three-phases windingswound around said stator salient poles; a rotor rotatable held insidethe said stator; and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said windings of each phase havea phase difference of voltage between at least one of the windings andthe other.
 2. A permanent magnet rotating electric machine according toclaim 1, wherein M:P=6n:6n±2 is satisfied where M is the number of saidstator salient poles, P is the number of said permanent magnets, and nis a positive integer.
 3. A permanent magnet rotating electric machineaccording to claim 1, wherein M:P=3n:3n±1 is satisfied where M is thenumber of said stator salient poles, P is the number of said permanentmagnets of said rotor, and n is a positive integer.
 4. A permanentmagnet rotating electric machine according to claim 1, wherein thenumber of poles of said permanent magnets is eight or more.
 5. Apermanent magnet rotating electric machine according to claim 1, whereina magnetic pole piece area of said rotor is projected toward saidstator.
 6. A permanent magnet rotating electric machine comprising: astator having stator salient poles, three-phases windings wound aroundsaid stator salient poles; a rotor rotatable held inside the saidstator; and permanent magnets inserted into said rotor and positionedopposite to said stator salient poles, wherein said three-phase windingsare concentratively wound around each of said stator salient poles.
 7. Apermanent magnet rotating electric machine according to claim 6, furthercomprising a magnetic material having a higher magnetic impermeabilitythan said permanent magnets disposed between adjacent ones of saidpermanent magnets.
 8. An electrically driven vehicle comprising: apermanent magnet rotating electric machine being coupled to drive wheelscomprising: a stator having stator salient poles, three-phases windingswound around said stator salient poles; a rotor rotatable held insidethe said stator; and permanent magnets inserted into said rotor andpositioned opposite to said stator salient poles, and control means forsupplying a voltage to said three-phase windings, wherein saidthree-phase windings are concentratively wound around each of saidstator salient poles, said windings of each phase are wound around atmore than one stator salient pole, and said control means suppliesvoltage which has a phase difference between at least one of thewindings and the other among each phase of three-phase.